1. Field of the Invention
The present invention relates to a substrate processing method which comprises immersing a substrate such as a semiconductor wafer, a glass substrate for a liquid crystal display device and a substrate for an electronic component in pure water stored in a processing bath to rinse the substrate with the pure water, exposing the substrate by pulling up out of the pure water or by draining the pure water from the processing bath, supplying a water-soluble organic solvent vapor such as an isopropyl alcohol (IPA) vapor to the substrate in the exposing step, and then drying the substrate under reduced pressure. The invention also relates to a substrate processing apparatus for use in executing the substrate processing method.
2. Description of the Background Art
Examples of a method of drying a substrate, e.g. a silicon wafer, after the wafer is rinsed with pure water in the process of manufacturing a semiconductor device include a spin drying method, an IPA vapor drying method, and a reduced-pressure pull up drying method using a water-soluble organic solvent vapor such as an IPA vapor. In recent years, the reduced-pressure pull up drying method has become mainstream. The reduced-pressure pull up drying method comprises: immersing a wafer in pure water stored in a processing bath to rinse the wafer with the pure water; pulling up the wafer out of the pure water in the processing bath (or draining the pure water from the processing bath, with the rinsed wafer held stationary in the processing bath) after the immersing step to expose the wafer from the pure water; supplying an IPA vapor to the wafer using an inert gas, e.g. nitrogen gas, as a carrier gas in the exposing step to condense the IPA vapor at a vapor-liquid interface on the surface of the wafer, thereby causing IPA to displace pure water deposited on the wafer surface; evacuating an enclosed processing chamber in which the processing bath is provided to a reduced pressure to vaporize the IPA condensed on the wafer surface, thereby rapidly drying the wafer.
FIG. 4 is a schematic view showing a general construction of a substrate processing apparatus for use in executing the reduced-pressure pull up drying method. This apparatus comprises a processing bath 102 in an enclosable processing chamber 100. Pure water supply means not shown supplies pure water into the processing bath 102, and a wafer W is immersed in and rinsed with pure water 104 filling the processing bath 102. Blast nozzles 106 are provided in an inner top portion of the processing chamber 100. The blast nozzles 106 supply nitrogen gas for purging the interior of the processing chamber 100, and supply an IPA vapor to the wafer W using nitrogen gas as a carrier gas when pulling up and drying the wafer W.
A gas/liquid discharge outlet 108 is provided in a bottom portion of the processing chamber 100, and is connected in communication with a gas/liquid discharge pipe 110. The gas/liquid discharge pipe 110 is connected in communication with an exhaust pipe 112, a water drainage pipe 116, and a liquid drainage pipe 120. The exhaust pipe 112 is provided with an open/close control valve 114 inserted therein which is opened when placing the interior of the processing chamber 100 under reduced pressure. The water drainage pipe 116 is provided with an open/close control valve 118 inserted therein which is opened during the rinsing of the wafer W with water, and drains the pure water overflowing from the processing bath 102 down to an inner bottom portion of the processing chamber 100. The liquid drainage pipe 120 is provided with an open/close control valve 122 inserted therein which is opened during the supply of the IPA vapor to the wafer W, and drains drainage liquid containing IPA.
Although the above described reduced-pressure pull up drying method is capable of drying a wafer using a small amount of IPA, further reduction in the amount of IPA consumption has been required from the viewpoint of recent environmental issues. In the conventional substrate processing apparatus, however, the IPA vapor supplied from the blast nozzles 106 to the wafer W flows from the interior of the processing chamber 100 via the gas/liquid discharge pipe 110 into the liquid drainage pipe 120, and is drained through the liquid drainage pipe 120. This presents the problem of consumption of more IPA than necessary.
Further, since the liquid drainage pipe 120 has an outlet of the IPA vapor, the state of atmosphere in a wafer drying zone within the processing chamber 100 becomes unstable under the influence of the operating status of utilities in a factory to which the liquid drainage pipe 120 is connected. Besides, there arises a difference in state of atmosphere between apparatuses, depending upon installation circumstances of the apparatuses. The conventional substrate processing apparatus has the problem of the lack of stability of wafer drying performance, coupled with the increased complexity and size reduction of a structure of a semiconductor device.
The present invention is intended for a substrate processing apparatus for supplying of an organic solvent vapor to a substrate exposed from pure water to dry the substrate.
According to the present invention, the apparatus for performing predetermined processing on a substrate, comprises: a substrate exposing section for exposing a substrate from pure water stored in a processing bath disposed in a processing chamber; a vapor supply section for supplying a water-soluble organic solvent vapor to the substrate; an evacuating section for evacuating an interior of the processing chamber; and a pressure regulating section for regulating pressure in the processing chamber at a fixed pressure when the organic solvent vapor is supplied to the substrate, the fixed pressure being higher than atmospheric pressure and remaining within a limit for maintenance of supply of the organic solvent vapor.
In the apparatus according to the present invention, the pressure regulating section regulates the pressure in the processing chamber at the pressure higher than atmospheric pressure when the organic solvent vapor is supplied to the substrate exposed from the pure water in the processing bath within the processing chamber. This reduces the amount of organic solvent vapor flowing out of the processing chamber. Additionally, the regulation of the pressure in the processing chamber at the fixed pressure stabilizes the state of atmosphere in a substrate drying zone in the processing chamber.
Preferably, according to a first aspect of the present invention, the apparatus further comprises a liquid drainage pipe for draining a drainage liquid containing an organic solvent flowing out of the processing chamber, wherein the pressure regulating section comprising: a buffer tank inserted at some midpoint in the liquid drainage pipe and having an enclosed structure, the buffer tank including an inlet and an outlet, the inlet being disposed above the outlet, the buffer tank having an interior vertically divided into a drainage liquid incoming compartment and a drainage liquid outgoing compartment, the drainage liquid incoming compartment and the drainage liquid outgoing compartment being in communication with each other at a position lower than the outlet; a vapor discharge pipe connected in communication with the drainage liquid incoming compartment of the buffer tank; and a pressure regulating valve inserted in the vapor discharge pipe.
In the apparatus according to the first aspect of the present invention, a flow path portion of the liquid drainage pipe which is upstream of the buffer tank and the drainage liquid incoming compartment of the buffer tank provide communication between the interior space of the processing chamber and the vapor discharge pipe. A partition inside the buffer tank and the drainage liquid stored in an inner bottom portion of the buffer tank up to the level of the outlet interrupt communication between the interior space of the processing chamber and a flow path portion of the liquid drainage pipe which is downstream of the buffer tank. Thus, the organic solvent vapor flowing out of the processing chamber does not flow to the flow path portion of the liquid drainage pipe which is downstream of the buffer tank, but flows out through the vapor discharge pipe. Controlling the pressure regulating valve inserted in the vapor discharge pipe to regulate the pressure in the processing chamber at a pressure higher than atmospheric pressure reduces the amount of organic solvent vapor flowing out of the processing chamber through the vapor discharge pipe. Additionally, controlling the pressure regulating valve to regulate the pressure in the processing chamber at the fixed pressure stabilizes the state of atmosphere in the substrate drying zone in the processing chamber. The drainage liquid containing the organic solvent stays temporarily in the inner bottom portion of the buffer tank, flows from the inner bottom portion of the buffer tank through the outlet into the liquid drainage pipe, and is drained.
Preferably, according to a second aspect of the present invention, the apparatus further comprises: a liquid drainage pipe for draining a drainage liquid containing an organic solvent flowing out of the processing chamber, wherein the pressure regulating section comprising: a vapor discharge pipe connected to the liquid drainage pipe; a trap inserted at some midpoint in the vapor discharge pipe; and a pressure regulating valve inserted in the vapor discharge pipe.
In the apparatus according to the second aspect of the present invention, the organic solvent vapor flowing out of the processing chamber flows out through the vapor discharge pipe connected to the liquid drainage pipe. Thus, controlling the pressure regulating valve inserted in the vapor discharge pipe to regulate the pressure in the processing chamber at a pressure higher than atmospheric pressure reduces the amount of organic solvent vapor flowing out of the processing chamber through the vapor discharge pipe. Additionally, controlling the pressure regulating valve to regulate the pressure in the processing chamber at the fixed pressure stabilizes the state of atmosphere in the substrate drying zone in the processing chamber. The drainage liquid containing the organic solvent collects in the trap, and is drained out of the trap as required.
The present invention is also intended for a method of performing predetermined processing on a substrate.
It is therefore an object of the present invention to provide a substrate processing method capable of reducing the amount of consumption of organic solvent such as IPA and improving the stability of substrate drying performance when performing a reduced-pressure pull up drying method, and to provide a substrate processing apparatus capable of preferably performing the substrate processing method.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.